Update: Engineers working on the shipwreck have declared the vessel upright after a 19-hour operation, reports the Associated Press.

Parbuckling is one of those terms like top kill, containment vessel or China Syndrome that you don’t learn until an oil rig blows up or a nuclear reactor goes down or something else goes terribly wrong. In this case the terribly wrong thing was the grounding and capsizing of the Costa Concordia, the 114,000-ton, 1,000-ft. long (304 m) cruise ship that foundered off the coast of Giglio, Italy in January 2012. Of the 4,200 passengers on board, 32 died; the bodies of two of them have never been recovered and are presumed to be on-board still.

Since the day of the accident, the ship has been laying sickly on its side, freakishly huge and half-submerged in the waters off Giglio, awaiting the day it could at last be raised and floated off for demolition. That day is today, and it’s parbuckling that makes the job possible.

From the start, engineers knew that the most straightforward way to dispose of massive wreck—cutting or blasting it to pieces and hauling it off bit by bit—would be neither safe nor sensible. There were 200 tons of fuel oil and lubricants aboard the ship and even after they were drained away in March of 2012, a witch’s brew of other toxins remain, including insecticides, paint, paint thinners and lubricants, as well as 1,000 gallons (3,900 liters) of gaseous carbon dioxide. And none of that includes the 26,000 lbs. (12,000 kg) of rotting cheese, beef and chicken and the 1,800 gal. (6,850 liters) of rancid milk products. A toxic mess like that meant that raising the boat whole and sailing it was the only option left.

The technique for doing that—which was mastered by the U.S. in 1943 when the USS Oklahoma was raised, two years after the Pearl Harbor attack—required first constructing a derrick-like tower in the shallow waters off Giglio, closer to the shore than the ship itself. Thick cables were attached to the ship so that when motorized winches on the derrick began turning, the 114,000 mass would be dragged slightly shoreward, unsticking it from the rocks and mire that have held it for the last 20 months.

Welded to the exposed flank of the ship are huge, hollow watertight boxes, called caissons, which all by themselves weigh over 11,000 tons. When the caissons are flooded with seawater, they should exert a downward pull on that side of the ship, causing it to roll slowly from its side into an upright position. When it does that, it will come to rest on a huge metal platform that has already been built underwater to hold it. Other cables and winches connecting the caisson side of the ship with the outer edge of the platform will provide an additional pull that will help the ship straighten up.

Swell, so now you have an upright wreck instead of a capsized wreck, and one that actually weighs 11,000 tons more than it did before. But caissons that can be filled with water can also be drained and filled with air. And once that is done both to the ones that are already attached to the ship and others that will be welded to the newly exposed side, the Costa Concordia should float off its platform, allowing it to be towed—very, very carefully—to an as-yet undisclosed place where it can at last be demolished.

The first step in the parbuckling process, the winching by the derrick, began this morning, but the ship didn’t budge until 6,000 tons of force were used. At that point, it finally pulled free. “We saw the detachment,” engineer Sergio Girotto told the Associated Press. What’s more, the Costa Concordia righted itself slightly, raising its head by just 3 degrees. It must roll another 62 degrees before it will be fully upright. That, the engineers say, should take 12 hours—if all goes well.

It’s a measure of how safe marine navigation has become that a parbuckling exercise like this one hasn’t had to be tried in 70 years. But it’s a measure too of the knife edge on which that safety record rests. The last time, it took Japanese war planes to make such a huge and complicated mess. This time it just took one careless captain who strayed too close to shore.

"Parbuckling" simply refers to turning any cylinder with ropes around it so as to produce a torsion. Shells for the 16" guns on battleships were "parbuckled" from the stationary part of the magazines to the rotating part of the turrets. And many other wrecked ships have been salvaged using parbuckling, it is not all that unusual and certainly has happened frequently in the last 70 years. Finally, the ship does not weigh 115,000 tons. That is its "gross tonnage," a measure of usable internal volume calculated with a mathematical formula. Its weight or "displacement is about 52,000 tons or less than half of the figure Time cites.